Egypt became the second African nation to qualify for the 2018 World Cup after defeating Congo 2-1 on Sunday evening.
However, the atmosphere was subdued and many fans shed tears when Congo's Arnold Bouka equalized with a half-volley after a defensive lapse with three minutes remaining.
His dramatic victor sparked wild scenes of celebration both on and off the pitch, as several players and fans took to the field to celebrate while supporters wept with joy in the packed stands. Just after the hour mark, Salah latched on to a pass from Arsenal's Mohamed El Nenny before poking home from close range.
The win clinched Egypt a long-awaited spot in Russian Federation for the 2018 World Cup finals, where the Arab world's most populous country will compete on football's ultimate stage for the first time since Italy in 1990.
Egypt got a reprieve in added time when substitute Mahmoud Hassan was brought and Salah restored the lead from the spot, sending the keeper the wrong way to clinch a place in Russian Federation next year.
Egypt ended the longest absence between appearances in two World Cups thanks to a last minute victor by Mohamed Salah.More news: American Wins Chicago Marathon, First Time Since 2002
Winger Mohamed Salah scored twice, securing victory with a last-gasp penalty to put Egypt four points clear with one match left in their African group E qualifying campaign.
Their latest attempt to do so had seen Argentine coach Cuper forced to take medication for high blood pressure.
The celebrations nearly got too much for goalkeeper Essam El Hadary.
The record was set by Colombian goalkeeper Faryd Mondragon, who played at the age of 43 at the 2014 World Cup, while El Hadary turns 45 next year.
Cuper says the challenge to qualify for Russian Federation 2018 FIFA World Cup ahead of him is so stressful, coupled with pressure from nation to deliver.